Alkylation process



Patented Sept. 10, 1946 2,401,585 ALKYLATION rnooass William A. Stover, Woodbury, N. 5., assignor to Socony-Vacuum Oil Company, Incorporated, a corporation of New York No Drawing. Application September ll, 1945,

Serial No. 615,695

12 Claims. 1

This invention relates generally, to the aikyla- I tion of parafiinic hydrocarbons with olefinic hydrocarbons, and is more particularly concerned with the production of high-octane motor fuels by the catalytic alkylation of paraffinic hydrohave been predicated upon the dictates of the chemical nature of the stocks available, as well as engineering considerations such as initial and operation costs; their essential feature being that in the course of treating the materials, the olefinic hydrocarbons produced in the earlier stages of the process, are eventually polymerized into hydrocarbons boiling within the gasoline boiling range, Accordingly, hydrocarbon gases may be passed along with cracking stock or naphtha through a cracking still to crack and polymerize such gases to gasoline simultaneously with the cracking or reforming, or parafinic hydrocarbon gases may be separately cracked into oleflnic hydrocarbon gases and these gases are subsequently passed with naphtha through a polymerizing and reforming still. In some instances, the processes involve the use of catalysts for facilitating the cracking and/or polymerization operations.

It is also well known in the art to combine parafilnic hydrocarbons directly with olefinic hydrocarbons by processes broadly called alkylation processes, to produce motor fuels having constituents of saturated character. In alkylation processes, a charge comprising a mixture of an alkylatable paraffinic hydrocarbon, called the paraffinic reactant, and an olefinic hydrocarbon, called the olefinic reactant or alkylating agent, is subjected to high temperature and pressure to produce a saturated alkylate product. Since conditions of alkylation also cause polymerizationof the olefinic reactant, it is necessary to maintain .a relatively low concentration of the olefinic reactant in the charge. The only limit to the pressure used appears to be the feasibility of maintaining high pressures. Onthe other hand, the temperature used is limited by degradation of the hydrocarbon reactants in the charge to low molecular weight hydrocarbons, and the occurrence of side, reactions, including polymerization of the oleflnic reactant, under high temperature conditions, that substantially reduce the Purity of the product obtained.

2 I'he temperatures and to a certain extent, the pressures employed in alkylation operations, depend upon whether the alkylation is effected in the absence or presence of alkylation catalysts. The two methods are generally referred to as thermal and catalytic alkylation, respectively. As is well known in the art, thermal alkylation ordinarily involves the use of temperatures of at least about 950 F. and pressures of the order of 4000 pounds per square inch or higher. At these temperatures, the degradation of the hydrocarbon reactants in the charge, and the occurrence of side reactions, including polymerization of the olefinic reactant, is somewhat marked. On'the other hand, catalytic alkylation involves the use of appreciably lower temperatures, thereby assuring a high yield of desired alkylate by avoiding extensive degradation of the reactants, the occurrence of secondary reactions, and appreciable polymerization of the oleiinic reactant.

Several methods are known for the catalytic alkylation of isoparafinic hydrocarbons with olefinic hydrocarbons. For instance, it is known to alkylate isoparafifinic hydrocarbons with olefinic hydrocarbons in the presence of sulfuric acid, phosphoric acid, meta1 phosphates, metal halides, activated clays and the like, as catalysts. In these catalytic alkylation processes, the hydrocarbon reactants form with the alkylation catalysts, a heterogeneous system during the alkylation operation. Hence, these alkylation catalysts may be termed heterogeneous alkylation catalysts. Since'under alkylation conditions, the catalytic activity ofthe alkylation catalysts appears to be predicated upon contact between the catalysts and the gaseous hydrocarbon reactants at the interfaces therebetween, in these processes, the catalysts are used in amounts varying between 10 per cent and 200 per cent by weight, on the charge, depending on the catalyst used. Due to these comparatively high amounts, where possible, recovery and regeneration of the catalysts have been proposed. This, of course, involves high initial and operation costs. Further, it is also known that certain substances called promoters,

promote the catalytic activity of these alkylation catalysts. Accordingly, several processes have been proposed wherein small amounts of these promoters, on the order of about 1 per cent to 3 per cent by weight on the charge, are added to the catalysts to promote their alkylation catalytic activity.

A copending application, Serial No. 502,018, filed September 11, 1943, is directed to the process of alkylating'normal paraflinic or isoparaffinic hydrocarbons with olefinic hydrocarbons, which comprises contacting a normal parafilnic or iso- .process of this copending application, comprise a broad temperature range of about 590 F.- to about 850 F., preferably, about 650 F. to about 825 F., and pressures of at least 500 pounds per square inch gauge, preferably, pressures of at least 1500 pounds per square inch.

Another copending application, Serial No. 502,813, filed September 17, 1943, is directed to the process of alkylating isobutane with propylene, which comprises contacting isobutane and propylene in a reaction zone under closely controlled alkylating conditions, with'promoter or small amounts of the homogeneous gaseous phase catalysts broadly disclosed-in the copending-application referred to hereinbefore, the closely controlled alkylating conditions including a temperature range of about 750 F. to about 850.F., preferably, about 775 F. to about 825 ,F., and pressures of at least 2500 pounds per square inch gauge. In the alkylation of isobutane with propylene in the presence of homogeneous gaseous phase alkylation catalysts, it was found that the alkylate obtained included constituents that are entirely different from the constituents of the hydrocarbon alkylate obtained in the alkylation of isobutane with propylene in the presence of known heterogeneous alkylation catalysts, i. e., AlCla, H2804, and the like. Thus, when heterogeneous alkylation catalysts are used, 2,3-dimethylpentane and 2,4-dimethylpentane are important constituents of the hydrocarbon alkylate obtained. On the, other hand, when homogeneous gaseous phase alkylation'catalysts are employed, triptane or 2,2,3-trimethylbutane, 2,2-dimethylpentane, and 2-methylhexane are the pre dominant constituents of the hydrocarbon alkylate. In this copending application, the formation of these three compounds was postulated as follows:

C Ha Ha C H; H Isobutane Propylene 2, 2, S-trimcthylbutan or triptane H CH:

Isobut ahe Propylene Z-methylhexnne From a motor fuel standpoint, the 2,2'-dimethylpentane .produced by the first reaction has] an octane number of about 93 CFR motor method; the Lriptane produced by the second reaction has an octane number of well over 100; and the motor fuels by the alkylation of isobutane with propylene, alkylation conditions that favor the production of triptane obviously are preferable.

It was also found that in actual practice, it was impossible to obtain triptane exclusively, appreciable amounts of 2,2-dimethylpentane and 2- methylhexane being always formed.

The specific classes of homogeneous gaseous phase catalysts disclosed in these copending applications are organic halogen compounds, and,

- more particularly, chlorine and bromine deriva- -tives of acyclic hydrocarbons.

Chloroform, chlorinated naphtha, chlorinated butane, carbon tetrachloride, ethylene .dibromide, propylene -di bromide, dibromisobutane, ethyl bromide, propylene tribromide, and tertiary monobromobutane are among the specific chlorine and bromine devention to provide an eflicient process for alkylating alkylatable isoparaflinic or alkylatable nor mal paraffinic hydrocarbons with olefinic hydrocarbons. Another .object is. to provide an improved process for catalytically alkylating either alkylatable normal parafilnic hydrocarbons or alkylatable isoparaflinic hydrocarbons with olefinic hydrocarbons. A more specific object is to provide a process for catalytically alkylating alkylatable normally gaseous isoparaffinic hydrocarbons with normally gaseous olefinic hydrocarbons, to produce high yields of high-octane gasoline. A very important object is to afford a process for alkylating isobutane with propylene, to produce high yields of high-octane gasoline. A further object is to provide a process capable of carrying out the above objects by using mixtures of carbon dioxide and water as homogeneous gaseous phase alkylation catalysts. Other objects and advantages of the present invention finic in nature and is substantially free from 2-methylhexaneobtained in 'the third reaction has an octane number of about 45. In View of will become apparent to those skilled in th: art from the following description. v

Broadly stated, my invention provides a process for alkylating alkylatable normal parafllnic or isoparaflilnic hydrocarbons, particularly isobu-' tane, with olefinic hydrocarbons, particularly propylene and ethylene, which comprises contacting the parafiinic and olefinic hydrocarbons in gaseous phase and in a reaction zone under alkylating conditions, with mixtures of carbon dioxide and water.

An important feature is the relatively low temperature that may be used.- As a result, degradation of the hydrocarbon reactants in the charge to low molecular weight hydrocarbons and the pronounced occurrence of side reactions, including polymerization of the olefinic hydrocarbons, are substantially completely avoided. Consequently, in my process, I obtain high yields of a high grade product that is almost entirely parafimpurities.

A very important feature of the present invention is the fact that, contrary to known catalytic ,alkylation processes of the prior art in which the hydrocarbon reactants being processed form with the alkylation catalysts, a heterogeneous as heterogeneous alkylation catalysts.

'atable parafiinlc hydrocarbons.

system during the alkylation operation, the alkylation process of my invention, employs alkylation catalysts consisting essentially of materials that form with the hydrocarbon reactants being processed, a single, homogeneous gaseous phase under alkylating conditions. The

'alkylation catalysts of the present invention are called, therefore and as noted hereinbefore, homogeneous gaseous phase alkylation catalysts, in contradistinction to the alkylation catalysts of the prior art which are referred to Accordingly, as a result of the catalysts being in the same phase or state as the hydrocarbon reactants being processed, fouling of the catalyst is substantially eliminated and agitation and/or mixing problems are non-extant. Further, since the catalytic activity of alkylatlon catalysts appears to be predicated somewhat upon contact between the catalysts and the hydrocarbon reactants at the interfaces therebetween, it follows that the catalytic efficiency of a given catalyst increases with the increase in area of interfacial contact, other variables remaining constant. Hence, since the homogeneous gaseous phase alkylation catalysts of my process inherently furnish the greatest possible interracial contact" between the catalyst and the hydrocarbon reactants under the conditions of allrylation, eficient catalytic activity with a concomitant high yield of high grade alkylate is possible although using relatively small amounts of homogeneous gaseous phase alkylation catalyst.

In view of the foregoing, an operation feature of the process of the present invention that is of considerable practical importance, is that relatively small amounts of carbon dioxide and water may be .used as allrylaticn catalysts. These amounts are so small and the materials are so cheap that they may be discarded feasibly, thereby obviating recovery and regeneration problems and eliminating high initial and operation costs. The amounts of carbon dioxide and water used in my process may vary between about 3 per cent by weight and 50 per cent by weight, and between about 3 per cent by weight and 50 per cent by weight, respectively, and preferably, between about 5 per cent by weight and 20 per cent by weight, and about 5 per cent by weight and about 20 per cent by weight, respectively, with respect to total charge of hydrocarbon reactants. It must be noted, however, that larger amounts of each may be employed if desired, although no additional advantages seem to result therefrom.

The paramnlc and olefinic hydrocarbons to be used in my process may be derived from any suitable source, as is well known in the art, and may be used either in the pure state or in admixture with other constituents not undesirable. The paramnic and olefinic hydrocarbons usually employed in the preferred operation of manufacturing motor fuels, will be the normally gaseous-pan ammo hydrocarbons, except methane and ethane, and the normally gaseous olefinic hydrocarbons, as is well understood in the art. Here again this process has a distinct advantage over many of the prior art processes, in that the olefin ethylene may be used for alkylating the alkyl- It is well known that ethylene cannot be used in many catalytic processes, including the sulfuric acid process, whereby the supply of available olefinic hydrocarbons is restricted. Therefore, an important aspect of the present invention is the fact that isobutane, for instance, may be aikylated with ethylene. I

A conventional and preferred source of paraffinic and olefinic hydrocarbons is the iixed gases 5 obtained around petroleum refineries. These fixed gases may furnish substantially all the desired parafilnic and olefinic hydrocarbons, or it may be necessary or desirable to obtain additional supplies, as is well understood. Additional olefinic hydrocarbons, if required, may be formed from a portion of the parafinic hydrocarbons. flnic hydrocarbons may be admixed to increase the concentration of paraflinic hydrocarbons to a desired magnitude.

In carrying out my process, I use temperatures varying between about 590 F. and about 850 F., and preferably temperatures varying between about 650' Hand about 825 F. In the allcylation of isobutane with propylene, however, it was found, as disclosed in copending application Serial No. 502,813, filed September 17, 1943, that the best yields of desired alkylate are obtained when the alkylatlon is conducted at temperatures falling within about 750 F. to about 850 F., and

preferably within about 775 F. to about 825 F.

The alkylate produced under these conditions contains no more than 5 per cent of oleiinic hydrocarbons and no aromatics so that the predominance of alkylation obtained thereby is a distinct feature of the process. Under appreciable higher temperature conditions, secondary reactions occur that substantially reduce the purity of the product obtained. In the alkylation of lsobutane with propylene in accordance with the process of the present invention, it must be noted that even within the preferred temper-, ature range, side reactions occur that account for substantial portions of the total allrylate.

40 The pressure to be used in my process may vary from about 500 pounds per square inch to about 6000 pounds per square inch or more, and preferably from about 2500 pounds per square inch to about 6000 pounds per squareinch, the

most suitable pressure being more or less dependent upon th particular temperature involved. In general, the higher the pressure, the higher the yield of alkylate. Accordingly, the criterion I for establishing an upper limit to the pressure 59 range used is primarily the feasibility of maintaining such pressure.

The process may be carried out as a batch, continuous or semi-continuous type of operation. Particularly when the process is carried out on a commercial scale, economic considerations make it preferable to operate in a continuous manner.

For emcient operation, whether the process is carried out on a batch or continuous basis, it is essential that the hydrocarbon reactants be intim mately contacted with the homogeneous gaseous phase catalysts of my invention. This may be efiected in several ways, as is Well known in the art.

In my process it is desirable, as in known isoparaffin-olefin alkylation processes, to keep the concentration of the olefinlc hydrocarbons relatively low during the alkylation reaction, in order to eliminate as much olefin polymerization as possible. Accordingly, it is advisable to maintain the olefin concentration inthe charge below about 25 per cent by volume, and preferably between about 5 per cent and about 12 per cent by volume. In continuous operation, this is effected by introducing the oleflnic reactant at a number of points in the reaction zone or by adding the On the other hand, additional parafables are more or less interdependent, hence.

when one is arbitrarily fixed, the limits within which the others may be varied, are somewhat restricted. In any particular instance, the most desirable conditions can be readily ascertained by one skilled in the art, the preferred ranges of these variables having been indicated hereinbefore.

The alkylate product that I obtain distills over 7 a fairly large boiling range, but 'a greater part of the alkylate, usually from about 85 per cent to about 90 per cent, distills in the boiling range of aviation gasolines. The iodine number of the aviation distillate is low, on the order of about 5 to 10. As mentioned hereinbefore, the alkylate product consists predominantly of branched parafilnic hydrocarbons.

Numerous experimental data could be adduced to indicate the results obtainable by employing the homogeneous gaseous phase catalysts of the present invention, but the following examples are sufficiently characteristic:

TABLE I Alkylation of isobutane with ethylene to produce neohexane Continuous operation Run'No.

Temperature, F 855 Pressure, lbs. per sq. in 2, 500 Contact time, minutes 10.0

Carbon dioxide, per cent by weight of hydrocarbon charge 6 Water. per cent by weight of hydrocarbon charge. 0 12.2 Ethylene, per cent by weight of l ydrocarbon'chargen 6. 4 5. 2 Volume per cent of alkylate boiling between 44 C.

and 54 C.- 36. 5 50. 6 Weight per cent of neohexane in 44-54 0. cut of alkylate 95+ 95+ TABLE II Alkylation of isobutane with propylene to produce triptane Continuous operation Run No Temperature, F 800 806 Pressure, lbs. per sq. in 4,500 4,600 Contact t me, minutes 15.3 16.8 Carbon dioxide, per cent by weight of hydrocarbon charge.- 0 7.0 Water. per cent by weight of hydrocarbon charge 0 11.5 Propylene, per cent by weight of hydrocarbon charge 10.3 10.1 Volume pe cent of alkylate boiling between 76 C. and 86 21.5 48.0 Volume per cent triptane in 7686 C. out of alkylate 11 6 This application is a continuation-in-part of my copending application Serial No. 523,727, filed February 24, 1944.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore desired that the present embodiments be considered in all respects as illustrative and not restrictive, reference being had to the appended claims rather than to the foregoing description to indicate the scope of the invention.

1 claim:

1. The process of alkylating alkylatable parafflnic hydrocarbons with oleflnic hydrocarbons, which comprises contacting an alkylatalble paraffinic hydrocarbon with an oleflnic hydrocarbon, in gaseous phase and in a. reaction zone under alkylating conditions, in the presence of a mixture of carbon dioxide and water, and maintain.- ing said alkylatable paraflinic hydrocarbon in excess over said olefinic hydrocarbon in said reaction zone, so that alkylation is the principal reaction.

2. The process of manufacturing a high-octane motor fuel, which comprises contacting an alkylatable normally gaseous parafllnic hydrocarbon with a normally gaseous olefinic hydrocarbon, in gaseous phase and in a reaction zone under alkylating conditions, in the presence of' a mixture of carbon dioxide and water, and. maintaining said alkylatable normally gaseous paraflinic hydrocarbon in excess over said normally gaseous olefinic hydrocarbon in said reaction zone, so that alkylation is the principal reaction. 7

3. The process of manufacturing a high-octane motor fuel, which comprises contacting isobutane with propylene, in gaseous phase and in a reaction zone under alkylating conditions, in

the presence of a mixture of carbon dioxide and water, and maintaining said isobutane in excess over said propylene in said reaction zone, so that alkylation is the principal reaction.

4. The process of manufacturing a high-octane motor fuel, which comprises contacting isobutane with ethylene, in gaseous phase and in a reaction zone under alkylating conditions, in the presence of a mixture of carbon dioxide and water, and maintaining said isobutane in excess over said ethylene in said reaction zone, so that alkylation is the principal reaction.

5'. The process of alkylating alkylatable paraffinic hydrocarbons with olefinic hydrocarbons, which comprises contacting an alkylatable parafiinic hydrocarbon with an olefinic hydrocarbon, in gaseousphase and in a reaction zone under alkylating conditions including a, temperature varying between about 590 F. and about 850 F.

carbon in excess over said oleflnic hydrocarbon in said reaction zone, so that aikylation is the principal reaction.

6. The process of manufacturing a high-octane motor fuel, which comprises contacting an alkylatabie normally gaseous isoparaflinic hydrocarbon with a. normally gaseous olefinic hydrocarbon, in gaseous phase and ma reaction zone under all rylating conditions including a temperature varying between about 590 F. and about 850 F. and a pressure of at least 500 pounds per 7 I squareinch, in the presence of a mixture of carbon dioxide and water, said carbon dioxide and said water each being present in amounts vary-v 

